Alzheimer's disease (AD) is a complex multi-genic neurodegenerative disorder characterized by progressive impairments in memory, behavior, language, and visuo-spatial skills, ending ultimately in death. Hallmark pathologies within vulnerable regions include extracellular .beta.-amyloid deposits, intracellular neurofibrillary tangles, synaptic loss, and extensive neuronal cell death. Research on the causes and treatments of Alzheimer's disease has led investigators down numerous avenues. Although many models have been proposed, no single model of AD satisfactorily accounts for all neuropathologic findings as well as the requirement of aging for disease onset. The mechanisms of disease progression are equally unclear. Considerable human genetic evidence has implicated alterations in production or processing of the human amyloid precursor protein (APP) in the etiology of the disease. However, intensive research has proven that AD is a multifactorial disease with many different, perhaps overlapping, etiologies.
To date, Alzheimer's disease is the third most expensive disease in the United States, costing society approximately $100 billion each year. It is one of the most prevalent illnesses in the elderly population, and with the aging of society, will become even more significant. Costs associated with AD include direct medical costs such as nursing home care, direct nonmedical costs such as in-home day care, and indirect costs such as lost patient and care giver productivity. Medical treatment may have economic benefits by slowing the rate of cognitive decline, delaying institutionalization, reducing care giver hours, and improving quality of life. Pharmacoeconomic evaluations have shown positive results regarding the effect of drug therapy on nursing home placement, cognition, and care giver time.
Thus far, the therapeutic strategies attempted have targeted neurotransmitter replacement, or the preservation of normal brain structures, which potentially provide short-time relief, but do not prevent neuronal degeneration and death. Thus, there is a need for therapies that prevent neuronal degeneration and death associated with Alzheimer's disease and provide long-term relief.